WKWebView 打开附件失败

web页面上面有附件，点击没反应，最后发现是需要实现以下代理方法

func webView(_ webView: WKWebView, createWebViewWith configuration: WKWebViewConfiguration, for navigationAction: WKNavigationAction, windowFeatures: WKWindowFeatures) -> WKWebView? {
        if navigationAction.targetFrame?.isMainFrame == nil {
            webView.load(navigationAction.request)
        }
        return nil;
    }